UDIN for Tax Audit in 2026: Five-Field Validation, Portal Gates and the Ceiling

A UDIN on a tax audit report used to tie the report to a member. Since December 2025 the e-filing portal also ties it to the assessee, and since February 2026 the UDIN portal asks about the audit before it issues one.

What changed, in order

• 20 June 2025. Information on the auditor's opinion becomes required when generating a UDIN under the GST & Tax Audit and Audit & Assurance Functions categories, in phases starting with Audit & Assurance Functions. It is not visible to third-party verifiers.
• 20 December 2025. The assessee's PAN becomes a mandatory field for UDINs under GST & Tax Audit, and the e-filing portal validates a UDIN on five parameters instead of four.
• 20 December 2025. A succeeding auditor must give details of the preceding year's audit when generating a UDIN under either category. ICAI says the information is confidential and not disseminated.
• 11 February 2026. Field-level validation runs for every sub-category under section 44AB(a) to (e), and a ceiling on UDINs in line with the limit of 60 tax audits is set from 1 April 2026.
• 1 April 2026. A one-time window, 1 to 30 April 2026, to generate UDINs for documents signed between 22 October and 22 November 2025, which could not be generated during the move to the new portal. For everything else, the rule of generating a UDIN within 60 days of signing continues.
• 8 June 2026. The category "GST & Tax Audit" is renamed "Tax Audit", and "Certificates" becomes "Certificates and Other Reports", following the Council's decision at its 446th meeting on 8 October 2025.

The five fields the e-filing portal validates

ICAI's announcement of 20 December 2025 lists them:

• MRN
• UDIN
• AY/FY
• Form No.
• PAN/TAN of the assessee

The UDIN is validated against all five, so the PAN, year and form number keyed on the UDIN portal have to be the ones on the report being uploaded. The PAN entered on the UDIN portal is not visible to any third-party verifier.

The questions asked before a UDIN is issued

The field-level validation table published with the 11 February 2026 announcement sets one gate per clause:

• 44AB(a), business: are cash transactions 5% or less? If yes, turnover must exceed ₹10 crore; if no, it must exceed ₹1 crore.
• 44AB(b), profession: gross receipts must exceed ₹50 lakh.
• 44AB(c): the portal proceeds only if the income claimed is lower than the deemed profits under section 44AE, 44BB or 44BBB.
• 44AB(d): it proceeds only if gross receipts are ₹50 lakh or less, or above ₹50 lakh but not above ₹75 lakh with cash receipts of 5% or less, and in either case the income claimed is lower than the deemed profits under section 44ADA and total income exceeds the basic exemption limit.
• 44AB(e): it proceeds only if section 44AD(4) applies and total income exceeds the basic exemption limit.

When an assignment fails its gate, ICAI's FAQs on the ceiling (Q10 and Q11) say it does not qualify as a tax audit for that sub-category. A UDIN is still mandatory, so it is generated under Audit & Assurance Functions, "Any other Audit not covered above".

The ceiling

The ceiling applies only to Form 3CA under the 3rd proviso to section 44AB, and to Form 3CB under section 44AB(a), section 44AB(b) and Combined. It is computed on the date the report is signed, adds together a member's UDINs across firms and individual capacity, and does not count revised reports. Changing a UDIN between a counted and an uncounted sub-category moves the count with it (FAQ Q9). The full counting rules, with a register that applies them, are in the 60 tax audit limit.

Before generating the UDIN

• Key the assessee's PAN, the assessment year and the form number exactly as they appear on the report to be uploaded.
• Pick the sub-category that matches the clause of section 44AB the audit is under, since the count follows the sub-category.
• Have the preceding year's audit details ready when taking over from another auditor.
• Diary the 60-day window from the date of signing.